There is an ongoing need for materials that may be used in orthopedic devices to enhance the quality of life of users of the devices by providing orthopedic devices that are more comfortable and that allow more normal body movement. In particular, there is a need for materials that are lightweight, breathable, and comfortable when placed in contact with the skin or close to the skin for long periods of time underneath a rigid outer cast or other orthopedic device. Breathability is desirable because it facilitates drying and the elimination of perspiration. This leads to the faster healing of wounds and minimizes skin maceration. Materials that do not absorb and retain moisture when immersed in water are also desirable, because the casts or other orthopedic devices can then be worn while the patient is bathing. It is also desirable that the materials can be washed if they are in a device where they are accessible or can be removed. Cotton fabrics and the like that are often used retain water and are thus unsuitable for washing or for use in water.
With respect to medical casts, materials that are currently used under the casts are generally in the form of a gauze, which may be stretchable, and which is wrapped in multiple layers to the desired thickness. The materials inside the cast are most often made of cotton or synthetic fibers, such as polyester, rayon, or acrylic. Other materials that have been used or are currently in use include polypropylene, fluoropolymers (GORTEX.RTM.), and cellulose acetate. Cast padding materials based on these materials are difficult to dry, in some cases because of the inherent difficulty in drying the material (e.g. cotton, because it is hydrophilic), and also because the physical form of the material restricts the rapid removal of water by drainage and evaporation.
Many approaches have been taken to overcome the problems associated with perspiration and moisture underneath a cast. For example, U.S. Pat. No. 4,539,982 teaches odor absorbing webs that are composed of a foam or bundles of cellulosic fibers and that also include activated carbon particles for the purpose of absorbing moisture and odor. Perforated poly(vinyl chloride) foam that allows moisture to pass through the perforations and that can pass moisture along the surface is taught in U.S. Pat. No. 4,516,572. This material is dried by heating when it gets wet. U.S. Pat. No. 5,540,964 teaches cast lining materials which are made from hydrophobic fibers that have been modified so that their surface is hydrophilic. These can wick moisture away from the skin. U.S. Pat. Nos. 5,102,711 and 5,277,954 teach a breathable, layered combination of microporous films and open cell foams.
The materials in these patents all deal with eliminating perspiration and moisture by using materials that wick away or absorb moisture. None of these patents provide the materials in a form that is open enough to allow for easy "breathing" under the cast for rapid evaporation. It would be desirable to have a material that can be used under a cast that feels soft and that has an open structure so that air and water can pass through easily. Such a material would allow the easy removal of water and easy drying. It would also feel cooler and more comfortable because of better air circulation.